We describe how an arousal system that controls the levels of awareness can be implemented in a robot. The different levels of awareness correspond to different states of consciousness and we argue that an artificial arousal system modeled after its biological counterpart has a useful function in controlling the cognitive processing of a brain-like cognitive architecture. The level of awareness depends on arousal that in turn is controlled by novel or emotionally charged stimuli as well as by a circadian clock. Arousal is also modulated during cognitive tasks to control the randomness of decision processes and to select between exploration and exploitation.